The major goal of this proposal is to understand how excitatory activity at glutamate receptors control the release and synthesis of vasopressin (VP) in magnocellular neuroendocrine cells (MNCs). Several subtypes of glutamate receptors are expressed on VP neuroendocrine cells and as in most other neuronal systems play a principle role in the control of excitatory activity. Pharmacological and oligonucleotide knockout approaches will be used on primary cultures of neuroendocrine cells to identify the role of NMDA receptor subunits NR2B and NR2C and metabotropic receptor subtypes mGluR1 and mGluR3 in the secretion of vasopressin and regulation of vasopressin mRNA and peptide content. By comparing release with changes in peptide and mRNA content under controlled conditions of stimulation, we will begin to understand how these three major steps in the release-synthesis cycle are coordinated. Interactions of osmotic, cell volume control mechanisms and extrinsic transmitter inputs with glutamate receptor activation will be examined in vitro and in vivo to better understand how glutamatergic activity is conditioned by these stimuli. The ability of each receptor subtype to mobilize two key second messengers, calcium and a novel c-jun kinase, will be examined in detail with digital video imaging and immunohistochemistry. These experiments will provide semi-quantitative data to characterize receptor actions at the cellular level and more clearly define the functional diversity of native glutamate receptor subtypes. The magnocellular neuroendocrine cells are ideal for such subtype-function studies since they have a dedicated, well define function and quantifiable output. Various actions of VP have been implicated in the control of cardiovascular regulation, stress responses, febrile seizures, CSF production, epilepsy, learning and memory, social attachment formations, Alzheimer's disease, and hypoxic ischemic brain damage. Basic principles revealed by the proposed studies will provide essential information about the function of NMDA and metabotropic glutamate receptor subtypes in normal and pathological processes across many disciplines.